Make interface argument optional

Not specifying an interface listens on all addresses. Since it is not
possible to determine the incoming address of a datagram, the SSDP
server looks up which interface would be used to send the reply when
constructing the reply.

Signed-off-by: Tyler Hall <tylerwhall@gmail.com>
HTTPThread: Honor interface argument

The HTTP server was listening on all addresses. Make it use the same
interface as the SSDP server.

Don't subclass Thread so we can use __init__ to set the interface
without having to call the parent's __init__.

Signed-off-by: Tyler Hall <tylerwhall@gmail.com>
Merge pull request #10 from tylerwhall/ipaddress

Make the listen address optional and consistent between the two servers